People never stay.

This is a well documented fact in Sherlock's life, expertly repeated with many examples. (Not on purpose, but that never seems to matter).

The first was Father. Sherlock was four and had made the mistake of asking why he was with another woman who wasn't Mummy. Mummy had heard him asking and then there was yelling and things thrown and slammed doors. Sherlock didn't understand why. He just wanted his question answered. Mycroft had pulled him aside and explained why he couldn't say things like that to other people. Father left the next day, never to return.

The next was Mummy. Oh, she never left physically, but emotionally it didn't make a difference. There were no more hugs, no more treats, no more 'that's my sweet boy' and twirls in the air. They had been rare before, but they had been there. Now he was passed from Nanny to Nanny. They never stayed long either, they couldn't stand him long, but didn't matter as much. He just didn't understand why Mummy didn't love him anymore.

Mycroft's leaving was inevitable. He knew this. He had to go to uni while Sherlock had to stay here, with all the stupid people in his school. The ones that laughed at him and pushed him and called him freak. He knew this. He was a big boy now, he didn't need his big brother to hold him and tell him that it wasn't his fault, that he was special and they were dull. He didn't. Still, the day after he left, he couldn't convince himself Mycroft wasn't happy to get away from him. Things were never the same after that.

Sherlock told himself it didn't matter when Sebastian Wilkes left him. He was an idiot and an arse. He was cruel and liked to play with people's emotions. He didn't matter. So what if he was the first person to show interest in his deduction skills. So what if he praised him and encouraged him to show off. So what if he made Sherlock feel like less of the freak he knew he was. He was just pretending. All he wanted were the answers to his homework. All he was was a parlour trick to increase Seb's popularity. He was happy when Seb left. He didn't matter.

Victor was different. When he said Sherlock wasn't a freak he meant it. When he said Sherlock's deductions were astonishing and neat and interesting they were. When he said Sherlock was amazing he was. He might, he could admit to himself, be a little bit in love with the other man. Never mind that they met because Victor's dog attacked him. Never mind the seven stitches he needed. Never mind any of that. Victor was Sherlock's first true friend. He became his first boyfriend. But he should have known it wouldn't last. It never did. Victor's father was ex (and then not-so-ex) Mafia and then he died and everything went up in smoke. He hasn't heard from Victor in years.

After that, he gave up. Alone is what he had. Alone protected him.

When Sherlock meets John Watson, he knows it is only a matter of time before he leaves as well. So what if he is only the second person not to tell him to 'Piss off'? So what if he says amazing and fantastic and brilliant out loud? So what if he shot a man for him only after 24 hours of knowing him? He won't last. They never do.

John continues to baffle Sherlock. It has been three months since he has moved in and and still he shows no signs of leaving. (The first time he walked out in a huff, because why put any effort into a relationship that is due to end eventually, he holds his breath. When John returns he lets out a soft relieved sigh. This is the first sign that he is in serious danger of falling yet again. Most likely with the same results.) He puts up with body parts and experiments and violin concerts and day(s) long silences and rude behavior and Mycroft. No gracefully, but he puts up with them.

When Jim Moriarty made John the fifth pip, he was sure this was the end. Either they would all die or they would survive and John would leave. What reason would he have for staying? He had already been expressing extreme displeasure with him. Sherlock had been preparing himself for the break. But they make it out and John still stays.

After Baskerville Sherlock lets himself believe that finally he has found a paradox in his theory. John Watson will be the one who stays.

Foolish.

The tears he cries on Barts are real. He falls to the ground below and gives himself a day to grieve the inevitable before he gets to work.

He returns after two years and finds he is correct. John has last the longest, but he is only human. He can only take so much before he is done. He still interrupts his attempt to propose to Mary even though it is a terrible idea because that is who he is. And besides, it's not like he can make it any worse. He has lost and he needs to extinguish his hope. When the cuts on his back reopen he tells himself he deserves it. When he treats his burns from the fire (fortunately his gloves have saved him hands, for the most part, if not his forearms) he tells himself it is worth it. When he tricks John into saying he forgives Sherlock it is because he needs to hear it, true or not (and it's not, no matter how much John believes himself when he says it). The case ends and he prepares himself never to see John Watson again.

But then John surprises him again. He shows up the next day to check up on him and stays for supper. When he leaves, Sherlock sits on the couch and realizes he is grinning like an idiot and shaking. He eradicates any hope his heart provides.

But something surprising happens. Days, weeks, a month, two, passes and still John has not officially proposed to Mary. They are still together, but John has made no move to try again. Sherlock can't understand it. It's not like Mary will say no. Only an idiot would turn John Watson down.

And John has had time. Sherlock has been making an effort not to bother John. He allows himself one text a day and one crime scene a week- a short one if possible, but not too boring. John will have better things to do now then hang out with his (surely) ex best friend. He is building a future for himself.

In fact it is now John who contacts Sherlock when he wants to get together. And as time passes it seems like that time increases. He will initiate their conversations over the phones and will drop by when he is free. Slowly their friendship rebuilds itself, becoming as strong as before.

Sherlock is torn between joy and despair. Joy because John still wants to be around him. He still wants him as a friend. Despair because it hurts. Things aren't the same as before. He has to watch himself around John, so as to not offend him too much. And the hope. The hope that he will come back to Sherlock. That things will be as they were before. He doesn't need more, no matter how much he may want it. He will take friendship and take it happily. But it won't last. History has shown that while John has an unusually high tolerance for him, he can be pushed too far. And after two years who knows where that line is now.

Besides, John has Mary now. Eventually John will propose again and Mary will say yes and they will get married and have a family. Then there will be no place for Sherlock at all in John's life. His lifestyle is not one a husband or father should keep.

So he tells himself over and over again that John Watson is not his to keep.

Until, one day, three months later John shows up at the flat. His emotions are sporadic, ranging from relieved and composed to nervous and fidgety.

"John?" he asks, "did something happen?"

"No, or yeah, but not that way. Can we talk?"

Sherlock feels the dread begin to creep in, but he nods. He deliberately stops himself from making further deductions, sure of what is coming. "Yes. Tea?"

John looks surprised. "Sure."

Sherlock goes into the kitchen and switches his kettle on. Over the years he has perfected the art of making his own tea. It's never as good as John's, but he makes due. He hands John his mug, just a way he likes it.

He takes it silently.

"Well?"

"Right. It's just... Mary and I broke up."

Sherlock furrows his eyebrows in confusion and surprise. "Why?"

"It was mutual. We've been talking and discovered we want different things. We thought it best to part ways before we did anything we regret."

Sherlock nods, still not understanding, but not wanting to ask. Obviously if John had wanted to explain more fully, he would have.

"Anyways, I was wondering if I could move back in?"

Sherlock's heart gives a painful thud. Stupid question, he wants to say, but doesn't. "Of course. You will always have a place here." Sentiment. Sentiment is important to John.

John smiles gratefully. "Thanks. Is it alright if I move today?"

"Of course." Sherlock can barely keep his emotions in check. John didn't propose to Mary. They broke up instead. John wants to move back in. John wants to be with him again. For however temporarily the time is, John wants to live with him again.

He mustn't mess this up. He must find a way to keep John for as long as he can.

"Right. I'm off to the flat to get my things. I'll be back soon."

Sherlock nods and watches him go out the doorway, down the stairs and through the door. It occurs to him then that maybe he should have offered his assistance... but no. He would have never offered before. And while he may want to keep John, staying in character is one of the key components to doing so. He can't act too odd or John might worry or suspect something is wrong and go into concerned Doctor mode. It is always harder to get John to drop something when he is like that. And he doesn't need to hear Sherlock's thoughts on this subject.

So he needs to act like before, but not too extreme. Demanding tea will be fine because John looked too shocked when he made it today. But no demanding John fetch him things like his phone or a pen. And he needs to use his own laptop. John was always displeased when Sherlock used his, even if he did resign himself to it. Experiments need to be contained and limited. Body parts on the assigned shelf. But they need to be present. John will never believe he gave them up entirely. No more violin after midnight- or anytime if John is asleep. Unless he is having a nightmare. Then it is acceptable as it helps him fall back asleep. And he must allow John to get a good night's rest as well. He must eat at least once a day and sleep every other day. This should be less of a problem because he tends to do that anyways since he has been back. Do not wake John up with his nightmares. Do not be silent for days on end. Do not ignore John when he is talking. Do not be rude (to John, everyone else are still idiots). Do not make a mess. Do not interrupt John's dates when he begins dating again.

Do not lose him again.

Sherlock nods to himself and begins to do some subtle cleaning.

John moves in and unpacks his things immediately. Then he comes down and goes into the kitchen to make himself a cup of tea. He makes another for Sherlock automatically. Sherlock watches this, thinking. Should he suggest food? John is sure to be hungry. Take out perhaps? Surely that won't seem too out of character. Or maybe it will. He never use to suggest for food unless a case had just ended. Best to let John ask.

He walks in and hands Sherlock his cup before he sits in his chair. Sherlock feels a coil of satisfaction settle in his stomach. It feels good to have John back, sitting in his chair, sipping tea out of his old RAMC mug, content to stay right where he is for now.

"Take out?" John asks.

"Mmm, yes."

"Chinese?"

"Fine."

John calls in their usual and drinks his tea until the doorbell rings. He goes down and gets their food. They eat in front of the telly, where Sherlock shouts abuse at the actors, but not too much. John enjoys some of his comments, but not all. Don't make too many.

After another couple of hours John gets up, wishes Sherlock goodnight and leaves for his room. Sherlock goes to his as well. He is too keyed up to sleep, but he finds he is much more comfortable in his room. It is smaller, feels safer. The living room only feels safe when John is there with him. Any other time it feels empty and cold. Too big for just one person. John fills it up.

He wants to play his violin. The music would soothe his erratic thoughts. He is terrible at processing emotions, especially his own. His violin helps him sort through and process them. But John is most likely asleep by now. He can't wake him up. He always complained before about the music when he was sleeping. So no, no music. Instead he tries to mediate, something he picked up in Tibet.

He stretches out on his bed and breathes deeply. His thoughts deliberately slow, calming down and quietly going into the designated section of his mind palace. Eventually there are none left, just peace and quiet. He falls asleep like that.

Slowly a routine forms, much like before. John works at the clinic, does the shopping, cleans the flat, makes sure they are both well fed and rested. In between he solves cases with Sherlock, goes on mad chases around London, tackles criminals and threatens to shoot people who threaten Sherlock.

For Sherlock, everything is different. His routine is set by limits. He can complain about boredom, but only so much. He can yell at the telly, but only every third comment can be said out loud and no ruining the plot. Body parts in the kitchen, but only large organs once a week and smaller ones three times. Explosions are out (or once a month, if he's being more realistic). No screeching on the violin, music only and only during daylight hours. He can interrupt John at the clinic, but only once a week. He can be an annoying git, but not to John and not too annoying to other people. He can argue with Sally and Anderson, but only if they start it. No going days without eating (he has to eat, he has to keep up his strength, never know when the next meal will come, never mind that no longer applies if it keeps John happy) or talking (no matter that some days he has to force himself, even if it is just grumbling). No panic attacks, no jumping at shadows, no flinching when John is around. No crying out in his sleep. No black circles under his eyes (it is a very good thing he has always been good with make up).

Despite all of this, despite the tediousness and the tiredness that from the consist battle to keep himself in check, Sherlock is happy. He is happy on days when there is no case- days when he would complain before- that he is content to lounge on the sofa with John sitting in his chair. He is happy when John gets home from work- finally, he wishes he would be home sooner, the flat is too empty without him, doesn't feel safe, but he can't know that, isn't in character- and orders take out and they watch crappy telly or a horrendous film John picked up on the way home. He is happy when he demands tea and John rolls his eyes, but still makes it and smiles his exasperated yet fond smile. He is happy to have John in his life.

So there are days of calm, days of adrenaline highs, days of exhaustion and days of exhilaration. Both men are satisfied with it.

So when John kisses Sherlock one day, after handing him tea, Sherlock's brain goes offline for a few moments. He didn't see it coming. Didn't observe. And isn't that ironic? The world's most observant man didn't know that his flatmate (his best friend?) wanted to kiss him. But how could he? He could never predict this outcome. After all, John isn't gay, he doesn't want this with Sherlock. He has made that clear in the past. But here he is now, kissing the detective.

It is a gentle kiss, a simple press of the lips. There is no tongue, no passion, nothing so many people talk about. Just fondness and tenderness and affection (...love...?). It makes Sherlock's heart pound.

"Alright?" John asks.

Sherlock nods, somewhat shakily.

John smiles. "Good. Now budge over, Doctor Who is on." He takes his place on the sofa beside Sherlock, shoulders and knees touching. Eventually he rests his head on Sherlock's shoulder and Sherlock cautiously puts an arm around him. John simply moves closer.

This is how John Watson starts his relationship with Sherlock Holmes.

Sherlock becomes even more elevated and fearful. Elevated because he could never imagine that John could want this, want him. He was no one's first choice for romantic partner, or even twentieth- he was the last and not even then would most people stoop so low. Fearful because when he loses John, he will lose so much more now. He will lose everything he ever hoped, ever dreamed for. Everything he ever wanted.

It became even more imperative to keep John Watson for as long as possible.

They take things slow. Sherlock lets John set the pace. And the pace John seems to want is slow. Not reluctant or nervous, but deliberately gentle and firm. Not passion, but affection and fondness. So much fondness it makes Sherlock's head spin some days.

It isn't what Sherlock is expecting to be honest. John is a very passionate person. It bleeds into everything he does. So why not this? Is it because he doesn't really want to be with Sherlock? But no, because he started this. Is it because he is a man? Maybe, but again, John was the initiator, so if he had doubts why begin this in the first place? Is it because this is the pace John think Sherlock wants? Is it because he thinks Sherlock is a virgin? He isn't, Victor took care of that years ago. This seems like a possible scenario, but if it is, John doesn't seem impatient. So maybe it is the pace John wants.

But slow pace or no, it is brilliant. There are cuddle on the couch, snogs in the alleyways and the kitchen and one time at the Yard. There are dates to restaurants and obscure sites in the city and the morgue- and John was the one who called that one a date, so no one can blame Sherlock of being a freak for that decision.

John is brilliant.

He is everything Sherlock dreamed of and hoped for. He is perfect. Well- as perfect as one can get while still being interesting. True perfection holds no interest for Sherlock. It's too dull, too predictable. John is anything but.

Sherlock has long ago accepted that he is head over heels in love for John Watson. He has known for years, even before the Fall. Their relationship merely confirms and reinforces the fact. But it also adds extra strain to him. The idea that he has to be perfect for John becomes embedded into his skin. Like the scars on his back, it brands him. Makes him vulnerable and fearful. Makes him aware of his every flaw and action.

The constant vigilance begins to wear on him. His nightmares become worse. So does his paranoia, his anxiety, his panic attacks. He seems to be sinking deeper and deeper instead of rising. He has done his best to keep it from John and thus far been fairly successful if not completely. He mustn't let John worry. John is suppose to be happy, not troubling himself over Sherlock's problems. He doesn't need to deal with them. Which is also why Sherlock plans on keeping his back hidden. He can't distress John or make him feel guilty. Or worse, have John say he deserves them.

John won't say that. Sherlock knows he won't. His Doctor is much too kindhearted for that. But maybe he will think it. Sherlock knows he can't stop himself from thinking it. From considering it part penance for what he did to John those two years away. From counting it as payment for getting to keep John just a little bit longer. He would face a hundred whips again if it meant John would stay with him.

But everyone has a breaking point. Even the Great Sherlock Holmes. And one day, he has finally reaches his.

He is experimenting in the kitchen when it happens. Two chemicals mix that shouldn't. A honest accident. One that seems to shake the entire flat.

"Sherlock!" John yells in surprise from the other room. "What the hell was that?"

When John comes stomping in, clearly put out, Sherlock is already on the ground, shaking. The explosion had taken him by surprise and he had hit his head on the way down, thoroughly disorienting him. He cowers away from John, no truly seeing him. "I'm sorry, I'm sorry, please don't, sorry, sorry, I'm sorry, please don't, please, please, please," he babbles on and on, all the while curling up as small as he can to minimize the damage that is sure to come. He begins to hyperventilate.

He feel a hand gently set on his back and flinches violently. "Please," he manages to whimper.

"Shh, hey now, shh, it's alright, everything will be fine, shh you're safe, you're safe. Just breath 'Lock, just breath," on and on and on as a gentle hand rubs circles on his back.

Slowly, ever so painfully and slowly, Sherlock comes back to himself. But he is still to shaken, still too nervous to fully comprehend the situation. Which is the likely explanation of why he doesn't shut up. "Sorry, I'm sorry John, please don't leave me. I'll be good. I'll be better. I promise. I can be good, I can. It was an accident, I promise, I promise it was. Please don't leave me. Please," he begs.

"Hey, hey, what is this?" John carefully pulls Sherlock into a secure embrace. "Why would I leave you?"

"Everyone always leave. I'm always too much. You've stayed so far, but even you have a breaking point. You can't reach it. You can't. I can't survive without you. Have to be good. Can't be too much. Can't be too loud. Can't worry you. Can't, can't, can't," Sherlock repeats, completely unable to stop himself.

"Oh Sherlock," John says, sounding immensely sad, "is that what you think? You have to act a certain way or I'll leave?" He runs a hand through sweaty curls.

"Everyone leaves," Sherlock reiterates, "everyone."

"Not me."

Sherlock shakes his head.

"Sherlock, you jumped off a building in front of me and I still came back. I feel secure in saying that nothing else you do can top that. Of course," he adds thoughtfully, "if you do it again I may kill you myself. But short of that," he shrugs.

Sherlock still shakes his head. He wants to believe John, he so badly does, but he has never been given a reason to doubt.

John sighs. Sherlock doesn't like it, John shouldn't be sad because of him. John deserves to be happy all the time, despite the impossibility of that goal. "I thought something was off," he mutters, "I just assumed," Sherlock feels him shake his head.

"Sorry," he whispers.

"Not your fault sweetheart, I should have said something sooner." He kisses him on the forehead. "I love you. You know that, yeah? I love you and I fell in love with you when you were an obnoxious git, I stayed in love with you when you were gone and I fell again when you came back despite any common sense. You are it for me Sherlock Holmes. You have been it seen the first day at Barts, I was just too blind to see it. Sorry to disappoint you honey bee, but at this point you are stuck with me. Can you believe that?"

No. Sherlock can't honestly say that he can. But now, on the floor, with a mess all around him and the panic finally draining from his system and John holding him securely in his arms and his confession in his ears, he thinks that one day he just might.

He wraps his arms around John in return, burying his head into his neck.

One day.